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Managing Post-Operative Pain in the Severely Obese Patient: Treatment and Monitoring Challenges

ASPMN 22nd National ConferenceSeptember 14, 2012

Maureen F. Cooney, DNP, FNP, BC

Denise Sullivan, MSN, ANP, BC

Obesity definitions

NHBLI, NIH http://www.nhlbi.nih.gov/health/public/heart/obesity/lose_wt/bmi_dis.htm accessed August, 2012

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Obesity

A state of chronic low grade inflammation

Adipose tissue secretes large amounts of cytokines (TNF, IL-6, vascular endothelial growth factor, interleukin-6) causing disturbance of the immune and metabolic systems

Inflammation may increase drug bioavailability

Pain Perception in the Obese vs. Non Obese

Limited number of studies

Contradictory results related to the impact of obesity on nociception. Nociceptive flexion reflex

Mechanical pressure

Needle pressure

Transcutaneous electrical nerve stimulation

Opioid requirement is variableLinares, C.L., Decleve, X, Opert, J.M….Mouly, S. (2009). Pharmacology of morphne in obese

patients.Clinical Pharmacokinetics, 48 (10), 635-651.

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Obesity’s Influence on Pain

Osteoarthritis, DJD most common pain syndromes

GERD (increased intra-abdominal pressure)

Gout

Fibromyalgia

Challenges of Obesity in the Surgical Patient

Ms. K-33 y/o woman with 18 hr history of constant severe right pelvic pain, no radiationNo aggravating/alleviating factors

Some nausea, no vomiting

PMH/PSH: Mild asthma; Para1/Grava1 c-sxn in 2010; appendectomy, age 17

Soc: smokes 1 pk/wk; denies ETOH, other meds

Meds: Medroxyprogesterone

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PE: 138/66, 96, 20 sat 95%, BMI: 34 Awake, alert, grimacing Neck supple Lungs clear, BS diminishes at bases NSR, no m/r/g + BS, 4 quads; guarding R lower quad, +

pain on palp, palpable mass RLQ, no rebound

GYN: no chandelier sign, Bimanual deferred d/t pain

Labs: WBC: 9.2; HCG negative

Ultrasound abdomen/ pelvis: fluid collection and right ovarian enlargement

CT abd/pelvis: adnexal mass/enlargement and intraperitoneal fluid collection

A: Acute pelvic pain, ruptured ovarian cyst vs ovarian torsion

P: Emergent Exploratory Lap

Perioperative Course

Induction: fentanyl 100 mcg and midazolam 2mg; Intraop: rocuronium, sevoflourane, fentanyl 150mcg, ondansetron, hydromorphone 2mg

Postop Open Ex Lap extubated in OR;

1100: To PACU with non-rebreather; 138/90-94-15-99%

arouseable with stimulation; Pain 4/10

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11:30 Converted to nasal cannula O2 @ 2L/min

Pain 6/10: Hydromorphone 0.5 mg q 15 min x 2 doses (last dose 11:45)

12noon: RR 9/min; O2 sat 95%; arouseable to strong tactile stimuli (Aldrette 1-2)

12:05 Unarouseable (Aldrete 0); RR 8/min O2 sat 88%

Pathophysiological Mechanisms leading to Pulmonary Complications

Pelosi & Gregoretti. (2011). Perioperative management of obese patients. Best Practice & Research Clinical Anaesthesiology, 24, 220.

Impact of Obesity on Respiratory Function

Reduced lung function with increased atelectasis

Derangements in respiratory system, lung, and chest wall compliance and increased resistance

Moderate to severe hypoxemia

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Impact of Obesity on Respiratory Function

Severe obesity: normal PaO2 while sitting up but reduced when supine

V/Q mismatch: lung bases well perfused, but hypoventilated up to 5% due to airway closure and alveolar collapse

Compliance is reduced due to effect of obesity on chest wall due to increase density and distribution of adipose tissue.

Most are eucapneic

RR is 40% higher in eucapneic obese compared to normal

Tidal volume reduced by 25% in OHS

Impact of Obesity on Respiratory Function

Risk factor for obstructive sleep apnea syndrome (OSAS), obesity hypoventilation syndrome(OHS), acute hypercapneic respiratory failure and respiratory post-surgical complications.

10% OSAS pts have daytime hypercapnea , some with pulmonary hypertension

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Obesity –Hypoventilation syndrome

Due to decreased lung volumes and reduced total lung compliance

Hypercarbia and hypoxemia while awake

Obstructive Sleep Apnea and Obesity

Obesity is a risk factor for OSA

Incidence of OSA increases in proportion to level of obesity

Prevalence of OSA in morbidly obese patient exceeds 70%

OSA found in 40% of obese females and 50% of obese males

Bell, R.L. & Rosebum, S.H. (2005). Postoperative considerations for patients with obesity and sleep apnea. Anesthesiology Clinics of North America, 23 , 493-500.

Polysomnography (PSG) is the “gold standard” for diagnosis of OSA

PSG may not be available to all and many go undiagnosed

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OSA, Obesity, and Opioids:Deadly Trio! Sedatives, opioid analgesics and

anesthetics alter airway tone

Chronic hypoventilation with mild hypercarbia in the resting preoperative state

Increased risk for aspiration and acute airway obstruction after extubation

Airway obstruction and death reported in OSA patients with minimal doses of sedatives and anesthetics

Postop risks in the severely obese

Greater risk of upper airway obstruction in sedated, obese patients from excess pharyngeal tissue.

May have sudden drop in PaO2 during periods of obstruction or decreased ventilation

Opioids and other meds associated with sedation and respiratory depression high risk in PACU.

Case Study Discussion:What happened to Ms. K? Patient concerns: morbidly obese;

asthmatic; active smoker; opioid naïve; abdominal pain

Increased risk for OSAS, obesity hypoventilation syndrome

Sedation, sudden decreases in oxygenation and respiratory depression may occur, particularly with the use of opioids

Risk of re-sedation from redistribution of anesthetics and analgesics from the adipose tissue to the blood stream

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Factors affecting pharmacokinetics

Increased adipose tissue

Increased blood volume

Higher cardiac output

Decreased total body water

Altered protein binding

Increased renal blood flow and glomerular filtration rate

Butcher, BJ. (2011). Acute pain management following Roux-en-Y gastric bypass surgery. Art & Science 31(12), 39.

Factors Affecting Tissue Distribution of Drugs

Affinity of drug for plasma proteins

Body composition

Regional circulation

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Circulation

3 ml of blood volume required to perfuse 100 g of adipose tissue, so blood volume increases with body weight.

Increased blood volume causes increased cardiac output and myocardial work load, potentially leading to cardiac failure and pulmonary edema.

Normal Blood Flow

5% to Adipose tissue

73% to viscera

22% to lean tissue

Alterations in Obesity

Only 2% to adipose

Viscera well perfused

Obesity increases both lean body mass and fat mass, but the percentage of fat increases more than the percentage of lean

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Increased circulating blood volume and higher than normal GFR which should increase the clearance of the drugs that are eliminated primarily by glomerular filtration.

Pharmacologic studies of renal function in obese patients provided varying results

Implications:

Muscle tissue holds more water than fat, so hydrophilic drugs should be dosed based on IBW.

Lipophilic: less predictable; if highly absorbed by adipose tissue, requires dosing based on TBW

Lipophilic: Due to decreased circulation to adipose tissue, may have decreased clearance, elimination half life may increase.

If normal renal function, will have increased drug clearance due to increased cardiac output; common co-morbidities (DM, HTN) often decrease renal function

Re-sedation Risk!

Re-distribution of lipophilic anesthetics or analgesics from adipose tissue to blood stream is possible!

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Recommendations:

Loading doses should be based on IBW when drug distribution is restricted to lean tissues

Loading doses based on IBW + % of TBW when distribution to lean tissue and partially to fat tissue

Loading doses based on TBW when distributed to lean and fat tissues or markedly in fat tissue

Maintenance doses depend on ability to clear medications. If CL is decreased, dose based on IBW

Morphine

Hydrophilic

Little or no change in volume of distribution with obesity; does not accumulate in adipose tissue

Dose to IBW

May be opioid of choice in obesity

Fentanyl

Lipophilic

Higher doses needed in obesity due to elevated volume of distribution compared with non-obese patients(

( Lotia and Bellamy, 2008).

Clearance higher and increases with TBW, but not a linear relationship

Administer infusions using IBW or LBW

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TBW 70 kgPKmass 64 kg

TBW 140 kgPKmass 100 kg

TBW 200 kgPKmass 109 kg

Remifentanyl

Ultra short acting, peak effect 1 minute

Pharmacokinetics not appreciably different in obese

Distributed less in obese, with less clearance

Dose based on LBM

Risk of severe bradycardia or hypotension if dose to TBW

Sufentanil

Distributed as extensively in excess body mass as lean tissue

Loading dose should account for total body weight (TBW)

Elimination is decreased in obese, so smaller maintenance doses

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Methadone

Lipophilic

Very high distribution on adipose tissue resulting in long duration of action and half life of 12- 150 hours

Midazolam

Lipophilic: Prolonged sedative effects

Inhibition of CYP450 3A4 by other drugs or obesity itself will reduce clearance

Continuous infusion rate should be adjusted to IBW to avoid oversedation

Daily discontinuation and re-titration to sedation scale target

Propofol

Highly lipophilic, rapid distribution to peripheral tissues

Short duration of action although longer than usual recovery times were reported after prolonged infusion

Maintenance dosing to TBW may lead to deep anesthesia and deleterious cardiac effects

Dose infusions to LBM

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Ketamine

Lipophilic

Use has been proposed in obese patients but study is limited

Ibuprofen

Pharmacologic data for ibuprofen suggest that doses may need to be increased without changing dosing intervals

Abernethy, D.R. & Greenblat, D.J. (1986). Drug disposition in obese humans. An update. Clinical Pharmacokinetics, 11, 199-213.

Challenges

Individuals with same BMI may have different body compositions and fatness; ethnic groups

Clinical situations may cause variation in hepatic metabolism of drugs

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The bottom line….

Hydrophilics are much more predictable.

Difficult to predict impact of obesity on pharmacokinetics of lipophilic drugs.

Monitor and titrate to effect!

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“Each drug may behave differently , and our present knowledge of the influence of obesity on pharmacokinetics is limited.“ (Cheymol, 2000)

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Management and Monitoring

Pain Management Recommendations

Anesthesiologist with special interest in anesthetic care and pain management should be identified to serve as interdepartmental liaison

Utilize opioid sparing multimodal strategies intraoperatively when possible

Avoid sedatives in combination with opioids

Schumann, R., Jones, S.B., et.al. (2005). Best Practice Recommendations for Anesthetic Perioperative Care and Pain Management in Weight Loss Surgery. Obesity Research. 13 (2), 254-266.

Schumann, R. Jones, S.B., Cooper, B., et. al. (2009). Update on best practice recommendations for anesthetic perioperative care and pain management in weight loss surgery, 2004-2007. Obesity. 17(5), 889-894.

Pre-Op Guidelines

Anesthesiology consult at least one day prior to surgery if possible

Assessment for sleep apnea-polysomnography for select patients

Smoking cessation at least 6 weeks before surgery

(Schumann, R., Jones, S.B, et.al. 2005)

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Intraoperative Anesthetic Management of the Patient with OSA

Avoid sedating premedication

Alpha-2 adrenergic agonist (clonidine, dexmedetomidine) may reduce intraoperative anesthetic requirements and have an opioid-sparing effect

Minimize use of opioids for analgesia; Use of short-acting agents (remifentanil)

Regional and multimodal analgesia (NSAIDs, acetaminophen, tramadol, ketamine, gabapentin, pregabalin, dexmedetomidine, dexamethasone)

Seet E., Chung F. (2010). Management of sleep apnea in adults - functional algorithms for the perioperative period. Can J Anesth. 57, 849-64.

Intraoperative Anesthetic Management of the Patient with OSA (cont.)

Use of regional blocks as a sole anesthetic technique

Use of intraoperative capnography for monitoring of respiration

Non-supine posture for extubation and recovery

Resume use of positive airway pressure device

Multimodal OR management produced less postop sedation in PACU, decrease in PCA morphine use

60 mg methylprednisolone preop 30 mg ketorolac before and at end of case 300-500 mcg clonidine during 1st hr of

anesthesia 100 mg lidocaine, then 4 mg/min for 1 hr,

then 3mg/min for second hr, then 2 mg/min for remainder of case

0.17 mg/kg/h ketamine infusion (max dose 1mg/kg)

80mg/kg magnesium sulfate

Feld J.M., Laurito, C.E., et al. (2003). Non-opioid analgesia improves pain relief and decreases sedation after gastric bypass surgery. Can J Anesth. 50(4), 336-341.

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MultimodalAnticonvulsants

Pregabalin 150mg prior to lap sleeve gastrectomy resulted in improved analgesia, opioid sparing and reduced adverse effects such as nausea and vomiting.

Cabrera Schulmeyer, M.C., de la Maza, J., et al. (2009). Analgesic effects of a single preoperative dose of pregabalin after laparoscopic sleeve gastrectomy. Obesity Surgery. 20(12), 1678-1681.

MultimodalAcetaminophen and NSAIDS

NSAIDS have a 30-50% opioid sparing effect Balestrieri, Simmons, et al. (1997); Ready, Brown, et al. (1994)

Ketorolac reduces opioid requirement in postop open and lap WLS Govindarajan, Ghosh, Sathyamoorthy, et al (2005).

Efficacy of ketorolac in lieu of narcotics in the operative management of laparoscopic surgery for morbid obesity. Surgery for Obesity and Related Diseases. 1, 530-536.

Multimodal approach with intravenous ketorolac and acetaminophen every 6 hours x 24 hours in bariatric surgery reduced opioid consumption by 41%. Time with an oxygen saturation below 90% reduced by 33.2% (Ziemann-Gimmel, ASMBS 2012 poster)

Multimodal Alpha 2 agonists

Preop oral clonidine in obese patients with OSA reduced anesthetic, intra and postop opioid requirements. Pawlick, Hansen,

Waldhauser, et al. (2005). Clonidine premedication in patients with sleep apnea syndrome, a randomized, double-blind, placebo-controlled study. Anesth Analg. 101, 1374-1380.

Postop clonidine bolus of 3 mcg/kg with continuous infusion of 0.3 mcg/kg/h with PCA morphine with significant analgesia, reduced morphine consumption, reduced n/v. Jeffes, Hall, Morris (2002)

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Multimodal Alpha 2 agonists

Intraop dexmedetomidine in open WLS has similar anesthetic and opioid sparing effect as clonidine. Feld et al (2006)

Dexmedetomidine in patients undergoing lap GBP resulted in better post op pain control and recovery profile with reduced opioid requirements.

Bakhamees, El-Halafawy, et al. (2007). Effects of dexmedetomidine morbidly obese patients undergoing laparoscopic gastric bypass. Middle East Journal of Anesthesiology. 19, 537-551.

Postoperative InterventionsGoals

Comply with respiratory physiotherapy

Early mobilization

Interventions Beach chair position (avoid supine)

Aggressive PT

Noninvasive respiratory support

Closely monitored fluid management and pain management

PCA Dosing� Modify for age & co-morbidities

especially sleep apnea

� Avoid basal infusions

� Weight: Consider lean body mass in dose calculation as adipose tissue serves as medication depot

� Prior opioid use: Larger doses, longer lockout interval

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Post-op Pain Control in Obese Patients

Premedicate with pregabalin (150mg 1hr pre-op, then q12)

Acetaminophen 1gm IV q6h or Celecoxib 200mg po q12h

IV PCA opioids-fentanyl 10mcg q 5 min lockout

Add Ketamine infusion @8-10mg/hr if pain not controlled

Schug, S.A., Raymann, A. Postoperative pain management of the obese patient. Best Practice & Research Clinical Anaesthesiology 25 (2011) 73-81.

RYGB Patient and Opioid Absorption

Liquid preparations are preferred

Avoid use of most long acting agents (may be possible if banding or sleeve with chronic pain)

Regional: Thoracic Epidural In comparison to opioids, better

spirometric values and faster recovery

Improves pulmonary function following abdominal surgery in obese patients. Von Ungem, Regli, Reber, Schneider (2005)

Improved analgesia and respiratory parameters after cardiac surgery compared to conventional opioid based analgesia Sharma, Mehta, et al. (2010)

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Regional: Thoracic Epidural

Thoracic epidural analgesia provided best analgesia in open GBPSchumann, Shikora, Wagner, et al. (2003)

Epidural solutions for postop OSA should be opioid free. ASA practice guidelines (2006)

Regional Anesthesia

6920 overweight or obese patients with a variety of blocks overall success rate 89% but if BMI > 30. 1.62 times more likely to have a failed block. Nielsen, Guller, Steele, et al. (2005)

Local anesthetic infiltration of wound is part of multimodal approach. Madan, Ternovits, Speck, Tichansky (2005)

RYGB patients with LA infusion sat up ½ day earlier and ambulated one full day earlier Lyer, Robertson, Lenkovsky et al. (2010)

Complementary Medicine

Lavender aroma therapy in morbidly obese patients in PACU in lap gastric banding Opioid sparing effect

Required less morphine in the immediate postop period Schug, Raymann (2011)

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Sentinel Alert Joint CommissionSafe Use of Opioids in Hospitals 8/2/12

Hospital opioid-related adverse drug events reported to The Joint Commission’s Sentinel Event database (2004-2011) 47% wrong dose

29% improper monitoring

11% other factors (excessive dosing, medication interactions, adverse drug reactions

“Various patients are at higher risk including patients with sleep apnea, patients who are morbidly obese, who are very young, who are elderly, who are very ill, and who concurrently receive other drugs that are central nervous system and respiratory depressants (e.g., anxiolytics, sedatives).”

http://www.jointcommission.org/assets/1/18/SEA_49_opioids_8_2_12_final.pdf

Monitoring

Intermittent “spot checks” of oxygenation (pulse oximetry) and ventilation (nursing assessment) are not adequate for reliably recognizing clinically significant evolving drug-induced respiratory depression in the postoperative period.

Continuous monitoring of oxygenation and/or ventilation of patients receiving opioids postoperatively.

Utilize capnography in patients requiring supplemental oxygen

Anesthesia Patient Safety Foundation (APSF), https://apsf.org/announcements.php?id=7ASA Taskforce Guidelines Perioperative Management of Patients with Obstructive Sleep Apnea (2006); Institute for Safe Medication Practices (ISMP)

ASPMN Nursing Guidelines on Monitoring for Opioid-Induced Sedation and Respiratory Depression (2011) Serial sedation and respiratory assessments are

recommended to evaluate patient response during opioid therapy by any route of administration.

Technology-supported monitoring (e.g., continuous pulse oximetry and capnography) can be effective for the patient at high risk for unintended advancing sedation and respiratory depression.

More vigilant monitoring of sedation and respiratory status should be performed when patients may be at greater risk for adverse events.

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Monitoring

Pulse oximetry for every patient with clinically significant obesity, suspicion of OSA using opioid analgesics and PCA

Alarms set for less than 90% saturation for 10 seconds

Gallagher, S., Haines, K. et al. (2010). Postoperative hypoxemia: Common, undetected, and unsuspected after bariatric surgery. Journal of surgical research, 159, 622-626.

Monitoring

Postop hypoxemia should be treated with early NIPPV Pelosi, Gregoretti (2010)

Utilize supplemental postoperative O2 despite acknowledged risk of prolonged apneic episodes and reduced detection of complications; this also results in increased SQ and wound-tissue oxygen tension in morbidly obese patients. ASA Taskforce Guidelines in OSA patients

Levi, D., Goodman, E, et al. (2003). Critical care of the obese and bariatric surgical patient. Critical Care Clinics, 19(1).

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Ms. K-33 y/o female s/p exp lapManagement

Patient stimulated; BVM with O2; Anesthesiology called and patient placed on BiPap

Naloxone 0.4mg in 9ml NS (40mcg/ml); 2ml administered every 2 minutes x 2 doses

Patient placed in high fowler’s position; frequent sedation and respiratory assessments

12:15 Arousable to verbal stimulation (Aldrete 1); RR 16/min; O2 sat 99%

Ms. K-33 y/o female s/p exp lapManagement

Initiate opioid sparing strategies Acetaminophen 1gm IV q 6h Intravenous ketorolac 30mg IV q 6h

Opioid changed to Morphine IV PCA 0 basal rate, 1mg PCA dose, 10 minute lockout

3:30pm: Alert (Aldrete 2); RR 18/min; O2 sat 100%; Pain 4/10

4p: Converted to nasal O2 @2L; capnography monitoring; continuous pulse oximetry

Ms. K-33 y/o female s/p exp lapMonitoring

Frequent sedation and respiratory assessments by nurse

Continuous pulse oximetry and capnography

Patient had two episodes of oxygen desaturation below 90%; O2 sat increased after stimulation; no further intervention was required

Patient transferred to Step Down Unit with continuous pulse oximetry and capnography

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Monitoring

Oxygen discontinued 12 hours post opNo further evidence of oxygen

desaturation on room air over the next 8 hours

Pain 4/10 with movement Transferred to general surgical floor

POD # 1Converted to standing oral ibuprofen and

prn oxycodone with acetaminophen

Take Home Points

Morbidly obese patients are at increased risk for OSAS and hypoventilation syndrome

Sedatives, anesthetics and opioids alter airway tone Re-distribution of lipophilic anesthetics or analgesics

from adipose tissue into circulation and the CNS may cause re-sedation

Dose opioids according to lean body mass Utilize opioid sparing strategies whenever possible More vigilant nurse assessment of sedation level

and respiratory status over the first 24 hours Early intervention with NIPPV

Thank You !